Onomondo SoftSIM for Nordic nRF91 Series

August 25, 2026 · View on GitHub

The Onomondo SoftSIM is an Open Source C based UICC implementation, allowing new and innovative cellular device designs to see the light of day in the ever-growing landscape of IoT!

To integrate this awesome new SoftSIM UICC form factor, we have partnered with Nordic Semiconductor to develop and distribute a new SoftSIM modem interface that supports APDU exchange between the modem and the application processor. For more details and an in-depth explanation, refer to Nordic Semiconductor's documentation.

This README is the quick path to a running sample. The full documentation — the design, every interface and configuration option, and how to adapt the SoftSIM to your own product or platform — lives in docs/.

Quick start

Initialize a workspace.
```
west init -m https://github.com/onomondo/nrf-softsim.git
git -C modules/lib/onomondo-softsim submodule update --init
west update
```
The git submodule step is required: west update does not initialize the manifest repository's own submodules, and without it lib/onomondo-uicc stays empty and the CMake configure step fails. To add the module to an existing application instead, see docs/integration.md.

Build and flash the sample.

cd modules/lib/onomondo-softsim/samples/softsim_external_profile
west build --sysbuild -b nrf9151dk/nrf9151/ns
west flash

Fetch a profile. Profiles are delivered through Onomondo's API, wrapped by the onomondo-softsim-cli. Generate an API key at app.onomondo.com/api-keys, then:
```
./softsim fetch --api-key <your_api_key> -n 1    # download 1 encrypted profile into ./profiles
./softsim next --key=<path to your private key>  # decrypt and print the next unused profile
```
softsim next guarantees a fresh profile on every call.
Provision the device. The flashed sample prompts on the UART (115200 baud): Transfer SoftSIM profile using serial COM port, terminate by newline character. Paste the softsim next output and press return. The device provisions, reboots and attaches:
```
<inf> softsim_sample: Profile received: <n> characters in total
...
<inf> softsim_sample: LTE connected!
```
Other delivery transports are covered in docs/provisioning.md.

That's it — at a glance, this is what you have just built and provisioned:

            ┌─────────────────────────────────────────────────────┐
            │         Application (your Zephyr software)          ├───────┐
            └──────────────────────────┬──────────────────────────┘       │
                                       │                                  │
                                       │  lte_lc_connect() / AT+CFUN=1    │  SoftSIM profile
                                       │                                  │  (onomondo-softsim-cli)
            ┌──────────────────────────▼──────────────────────────┐       │
LTE ~~~)))  │                     nRF91 modem                     │       │
            └────────────┬─────────────────────────▲──────────────┘       │
                         │                         │                      │
                         │  INIT · APDU ·          │  ATR · response      │
                         │  RESET · DEINIT         │  APDU + SW           │
                         │                         │                      │
            ┌────────────▼─────────────────────────┴──────────────┐       │
            │               nrf-softsim (this repo)               │◄──────┘
            │       modem glue · work queue · provisioning        │  nrf_softsim_provision()
            ├─────────────────────────────────────────────────────┤
            │            onomondo-uicc — the SIM core             │
            ├──────────────────────────┬──────────────────────────┤
            │  Storage port            │  Crypto port             │
            │  Zephyr NVS + RAM cache  │  PSA Crypto in TF-M      │
            └──────────────────────────┴──────────────────────────┘

License

The Onomondo nrf-softsim repository is provided under:

SPDX-License-Identifier: GPL-3.0-only

This repository is licensed under the terms of the GNU General Public License version 3 only, as provided in:

LICENSE